1. Field of the Invention
The present invention relates to a mouth guard composition for preventing teeth and their surrounding tissues from a trauma occurred mainly in sports.
2. Description of the Related Art
A large external force is often applied to teeth or a maxillary bone during the game of hard physical contact sports including boxing, rugby football and American football as well as soccer and karate. In order to confine a trauma on teeth and their surrounding tissues occurred at that time to the minimum and to protect a stomatognathic system, it is generally carried out to set in an oral cavity an elastic material made of, for example, rubber, which is called a mouth guard or a mouth protector.
For the mouth guard, various materials are used. Those that are most widely used at the present are polyolefin rubbers and ethylene-vinyl acetate copolymers as well as compositions comprising an ethylene-vinyl acetate copolymer having a thermoplastic polycaprolactone added thereto, as disclosed in Japanese Patent No. 2,594,830. These materials have elasticity, and their effects are superior. However, when a large external force is applied to such materials and that is repeatedly applied to the mouth guard, the materials themselves were broken when used only a few times. In particular, in preparing a so-called “custom-made” mouth guard that a dentist makes according to the shape of an oral cavity of an individual for whom the mouth guard is to be set, since the mouth guard is expensive, it is required to give to it a high durability. Accordingly, it was a problem that the mouth guard has been broken within a short period of time.
In order to improve these problems of the related art, the present applicant proposed, in Japanese Laid-Open Patent No. 2001-54610, a mouth guard having a superior durability because of its high tear strength, which is prepared from a composition comprising a styrene block copolymer, an alicyclic saturated hydrocarbon-based resin and/or an ester gum, and an organopolysiloxane in which at least one of organic groups directly bound to the silicon atom in one molecule thereof is a phenyl group, a methylstyryl group, or an alkyl group having 7˜30 carbon atoms, in predetermined proportions. However, not only tearing off on the occlusion surface but also worsening of the fitness caused by deformation of the mouth guard when the mouth guard is strongly chewed when it is set decreases the durability of the mouth guard. In addition, the thickness on the occlusion surface becomes thinner in use than it was originally designed, resulting in lowering an impact absorption force. Such problems occur due to a characteristic of the conventional mouth guards such that they likely generate plastic deformation when a strong occlusion force is applied. This characteristic is commonly found in the composition as disclosed in Japanese Laid-Open Patent No. 2001-54610, and hence, improvements have been demanded.
Moreover, when the conventional mouth guards are formed, a mouth guard composition provided in a sheet-like state is formed using a forming device while heating and sucking it. However, when the mouth guard compositions containing, as a major component, a polyolefin-based rubber or an ethylene-vinyl acetate copolymer, as currently used are used in the above-described method, such compositions were poor in forming properties due to a low fluidity after heating and softening, resulting in the production of incomplete mouth guards with poor fitness. Also, the mouth guards prepared from the conventional mouth guard compositions involved such a problem that when they are used repeatedly, their surfaces are most likely to be sticky by influences of saliva in an oral cavity, etc. becoming unsanitary, resulting in the generation of an offensive smell in use.